In addition, Athens acquired great wealth from the spoils of its wars and the tribute of its subject states. This wealth was expended largely in the beautifying of Athens, and in the consequent encouragement and opportunity to artists of all kinds. Naturally, the art most immediately encouraged was that of architecture; and that the encouragement met with ready and great success the most beautiful ruins in the world superbly testify. The directing genius in this work and in all the others was Pericles, who stimulated the Athenians with his conception and description of a city worthy to symbolize the power and glory of the empire. The twin arts of architecture and sculpture worked together and in harmony; and a city more beautiful than ever known before, or ever known since, testified to the soundness and brilliancy of the conception and to the constructive ability of the Athenians to embody it in material form. The poets and scholars kept pace with the statesmen and the architects and the sculptors; but the philosophers surpassed them all. For, while the successful democracy of Athens is a model still, and while the Parthenon and the statue of Apollo are models still, yet an integral part of the system of government (slavery) has been abjured by the civilized world, and the temples and the statues have been for the pleasure of but a few; while the teachings of the philosophers have been the basis on which has rested ever since much of the intellectual progress of mankind. It may be noted here that, as men have progressed up the steep road to civilization, the only guides they have had have been men who have not themselves passed over the road before, and whose only qualification as guides has lain in some attribute of the mind that enabled them to survey the road a little farther ahead than the others could, and to point out the paths to take, and the obstructions to avoid. Man's physical instincts guide him considerably as to the methods to preserve his physical existence; but they help him not at all to lift himself above his physical self, and in many ways they hinder him. It seems to be the office of the mind both to discern the upward paths and to stimulate the will to overcome the difficulties and dangers in the way.